/*
Copyright 2022 The KCP Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package shard

import (
	"context"
	"fmt"
	"io"

	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apiserver/pkg/admission"

	corev1alpha1 "github.com/kcp-dev/sdk/apis/core/v1alpha1"
)

// Default the external and virtual URLs with the base URL if they are not set.

const (
	PluginName = "tenancy.kcp.io/Shard"
)

func Register(plugins *admission.Plugins) {
	plugins.Register(PluginName,
		func(_ io.Reader) (admission.Interface, error) {
			return &shard{
				Handler: admission.NewHandler(admission.Create, admission.Update),
			}, nil
		})
}

type shard struct {
	*admission.Handler
}

// Ensure that the required admission interfaces are implemented.
var _ = admission.MutationInterface(&shard{})

// Admit sets.
func (o *shard) Admit(_ context.Context, a admission.Attributes, _ admission.ObjectInterfaces) (err error) {
	if a.GetResource().GroupResource() != corev1alpha1.Resource("shards") {
		return nil
	}

	u, ok := a.GetObject().(*unstructured.Unstructured)
	if !ok {
		return fmt.Errorf("unexpected type %T", a.GetObject())
	}
	wShard := &corev1alpha1.Shard{}
	if err := runtime.DefaultUnstructuredConverter.FromUnstructured(u.Object, wShard); err != nil {
		return fmt.Errorf("failed to convert unstructured to Shard: %w", err)
	}

	// If you reading this - this is probably not what you looking for.
	// Defaulting happens in pkg/server/config.go#L561, and these becomes no-op.
	// The only case where these will be used, if somebody is creating Shard
	// objects directly or using kcp as a library and skipping defaulting in config.go.
	// So if you not sure what is happening - its probably better to be explicit and set these flags.
	// But if you are doing that - you probably know what you are doing :)
	if wShard.Spec.BaseURL == "" {
		return fmt.Errorf("spec.baseURL is required")
	}
	if wShard.Spec.ExternalURL == "" {
		wShard.Spec.ExternalURL = wShard.Spec.BaseURL
	}

	if wShard.Spec.VirtualWorkspaceURL == "" {
		wShard.Spec.VirtualWorkspaceURL = wShard.Spec.BaseURL
	}

	raw, err := runtime.DefaultUnstructuredConverter.ToUnstructured(wShard)
	if err != nil {
		return err
	}
	u.Object = raw

	return nil
}
